Purpose(s) of Project

Develop sampling methods for Florida wetlands and utilize Geographic Information System (GIS) technology for regionalization and to quantify disturbance gradients.

Project History

The University of Florida Center for Wetlands is involved in a multiyear wetland research project funded by the Florida Department of Environmental Protection (FDEP) to develop an integrated biological approach for evaluating Florida's wetlands. The goal of the project is to develop an assessment approach that recognizes the utility of both biological and functional assessments, and is rapid, reproducible, and meaningful.

The Center for Wetlands began development of the assessment approach in 1997. Now in its third year, the project titled "Development of a Biological Approach for Assessing Wetland Function and Integrity," has four main tasks:

Task 1. Review and synthesize all current and relevant literature.

Task 2. Develop a wetland classification system for wetland types in the state of Florida.

Task 3. Develop a GIS-driven methodology for classifying bioregions within the state of Florida that identify climatic, geologic, and geophysical provinces that are sensitive to wetland classes.

Task 4. Develop a bioassessment methodology and a list of candidate biocriteria and metrics in the state of Florida.

Florida Wetlands
A freshwater marsh in central Florida, near Lake Kissimee. Photograph taken by Dave Davis

The development of the approach has included a review of technical and scientific literature, a wetland classification and crosswalk, wetland regionalization of Florida, and two wetland biological surveys in the summers of 1998 and 1999. The biological surveys were designed to test the validity (and necessity) of the proposed wetland regions, to identify the appropriate biological indicator taxa, and to quantify the disturbance gradient.

Study Design

The development of the approach included a review of technical and scientific literature, a wetland classification and crosswalk, draft wetland regions, and wetland biological surveys in 1998 and 1999.

The wetland classification scheme was organized with major classes defined from three variables:

An HTML electronic database has been completed that cross walks existing wetland classifications to the new simplified, classification scheme developed for the bioassessment project.

Regionalization of the state was necessary since there is significant variation in climatic and physical features of the Florida peninsula and it was believed that these regional differences will equate to variations in bioindicator "signals." Map coverages of physical and climatic variables of the Florida landscape were used to develop regions that had different characteristic driving energies and landscape structural characteristics.

The input coverages were utilized with GIS map algebra to create a spatial hydrologic budget equation for the state. The equation modeled the movement of water on the landscape during the ecologically sensitive spring growing season. The output of the model provided a value for a Potential Soil Moisture Index (PSMI). The PSMI was separated into four regions based on both the critical depth of saturation and on a statistical clustering of the PSMI values (see accompanying map). The classified regions were tested for similarities and differences to determine if between region variation in wetland type and environmental variables was greater than within region variations.

The importance of hydrology in determining wetland type and location (the premise behind the PSMI) was then tested using a hierarchical classification technique (TWINSPAN), and ordination (DCA and CCA) with variables of seasonal and annual rainfall, seasonal and annual potential evapotranspiration, slope, geology, drainage class, and runoff. TWINSPAN, DCA, and CCA tested the relationships between wetland type and climatic and physiographic landscape characteristics. Based on the geostatistical output, hydrology is indeed a major determinant of wetland type and location and supports the use of the spatial hydrologic budget equation in delineating wetland regions.

Two years of biological surveys of wetlands throughout the state were designed to test regionalization as well as for metric and bioindicator development. The 1998 pilot field research involved surveying 24 herbaceous and forested depression wetlands in north and central Florida. Major taxonomic assemblages were characterized and ranked along a gradient of disturbances. Sites were located within multiple land uses such as parks, preserves, pasture, farm fields, well fields, silviculture plots, and urban. Impacts that were assessed included hydrological modifications, nutrient loading, and altered hydroperiod. The first year's sampling resulted in development of standardized sampling procedures, design and implementation of a statewide sampling program, and identification of community attributes and candidate metrics.

In the second year's field season, 36 herbaceous, depressional wetlands were surveyed in three regions. Twelve sites were included in each of three regions: north, centralc and southern peninsular. Approximately half of the wetlands were impacted (agricultural setting) and half were reference locations. Many of the sites were paired sites (impacted and reference at close proximity). All sites were located with the aid of staff and personnel from various state and local government agencies. Several of the sites had previously been functionally assessed by hydrogeomorphic modeling (HGM). All sites will be evaluated using HGM.

Assemblages Monitored

Field Protocol

Surrounding land uses and wetland disturbances are characterized. Vegetation is surveyed along four transects aligned to the cardinal directions and intersecting in the center of the wetland if the wetland is small enough. All plants within a 1 m x 5 m belt transect are identified to species and presence noted. Unknown plants are pressed for later identification by a wetland plant expert. Macroinvertebrates are collected using D-frame dip net sweeps.

Sweep samples are preserved in the field and brought to FDEP Biological Lab for picking and identification. Fish captured in traps are identified, counted, and examined for deformities, ectoparasites, lesions, and tumors (DELTs). Unknown fish and organisms and those expressing a DELT are preserved for future identification and analysis. Algal samples are collected and preserved for intensive laboratory identification. Water quality samples are collected and sent to the FDEP's Chemistry Laboratory for analysis.

Quantifying Disturbance Gradients

A Land Development Intensity (LDI) index is being used to quantify disturbance gradients for wetlands in agricultural and urban landscapes throughout the state. The LDI index is calculated using land use/land cover characteristics of lands within a 500-foot buffer surrounding the wetland. Several different LDI indices are being calculated and evaluated for sensitivity. The LDI algorithm multiplies the percent area of each land use/land cover in the surrounding 500-foot buffer by several different coefficients. The coefficients are scaled from 1 to 10 and represent intensity of environmental manipulation or environmental impact. Three indices are being calculated for urban areas based on the following weighting factors: (1) degree of surficial groundwater alteration, (2) percent impervious surface, and (3) stormwater-runoff-event mean concentrations of phosphorus. The weighting is such that lower LDIs are indicative of a lower disturbance level.

In agricultural landscapes, the LDI is calculated using weighting factors based on intensity of agricultural activity. Native-range and low-intensity agricultural crops, such as hay fields, have values of 1 to 2. Vegetable crops depending on intensity of cropping system have values from 3 to 5. Improved pastures where cows have access to the wetland are weighted from 6 to 8. Very intense agricultural operations, such as dairy cattle and feed lots in close proximity to wetlands, are given weights of 9 to 10. The weighting is such that lower LDIs are indicative of a lower disturbance level.